Fabrication of integrated circuitry typically involves patterning and etching materials to form substrate features such as conductive lines. In many integrated circuitry applications, it is highly desirable to form conductive lines having standard or uniform conductive line widths, at least within a region of interest. Conductive line widths which vary between conductive lines can modify the conductive characteristics of the lines, and result in undesirable circuit performance. This problem can be of particular significance in the context of memory circuitry such as dynamic random access memory (DRAM) or static random access memory (SRAM) circuitry.
FIGS. 1 and 2 illustrate a typical processing scenario in which conductive lines having variable widths (and hence variable channel lengths) can be undesirably formed. Referring first to FIG. 1, a semiconductor wafer fragment 10 includes a semiconductive substrate 12. A conductive material layer 14 is formed over substrate 12 and an insulative material layer 16 is formed thereover. Conductive material layer 14 can comprise one or more conductive layers such as conductively doped polysilicon and/or a silicide, and insulative material layer 16 can comprise any suitable insulative material such as various nitrides and/or oxides.
A patterned masking layer 18 is formed over substrate 12 and defines a plurality of conductive lines which are to be subsequently etched from layers 14, 16. Each individual masking layer component has a generally uniform or constant length L which will be utilized to define, at least in part, the channel length/gate width of the subsequently etched conductive lines. In theory, the subsequent etching of the conductive lines from the patterned substrate of FIG. 1 should result in a series of conductive lines having a constant width or channel length. Such has not, however, been observed to occur with dry etching as L fell to and below 0.5 micron, as will become apparent from FIG. 2.
There, four conductive lines 20, 22, 24, and 26 have been etched from layers 14, 16. Yet, the conductive lines have variable widths and hence variable channel lengths in spite of having masking blocks 18 of the same dimension. Conductive lines 20 and 24 constitute "edge lines" which have no immediate conductive line neighbor on only one side thereof. Conductive line 22 comprises a "center line" which has immediate conductive line neighbors on each side thereof. Conductive line 26 comprises an "isolated line" which has no immediate conductive line neighbor on either side thereof.
Edge lines 20, 24 have widths which vary from center line 22 by a factor 6, thereby giving an effective channel length of L+.delta.. Isolated line 26 has a width, and hence a channel length, equal to around L+2.delta.. Conductive lines having immediately adjacent neighboring lines within a desired or selected distance, i.e. line 22, on each side thereof have generally uniform or standard widths and channel lengths. On the other hand, conductive lines which do not have immediately adjacent neighboring lines within a desired or selected distance on each side do not have standardized widths or channel lengths, i.e. lines 20, 24, and 26. Accordingly, it would be desirable to eliminate the variability of conductive line widths and hence channel lengths as described above.
This invention arose out of concerns associated with providing improved semiconductor design methods and processing methods directed to providing improved uniformity between conductive line widths and channel lengths.